1. Technical Field
The present invention relates generally to a piston structure for an internal combustion engine, and more particularly to an improved rib reinforcement to provide a necessary rigidity to a piston skirt.
2. Background Art
A piston structure is well known in the art which includes a uniformly wide rib reinforcement extending around the inner peripheral surface of a piston skirt on a plane perpendicular to the centerline of a piston. This rib reinforcement is positioned at a lower portion of the piston skirt and adjacent the bottom of a pin boss into which a piston pin is inserted to attach a connecting rod. The piston further includes a slipper portion extending below the rib reinforcement for reducing noise or wear thereof due to reciprocating motion of the piston during combustion.
However, in the above conventional piston structure, because the uniformly wide rib reinforcement extends horizontally with respect to the piston stroke, provision of the slipper portion is necessary below the piston skirt to absorb side thrust acting on the piston during combustion for reducing the noise and vibration. It will be appreciated that the piston is lengthened and the weight thereof is increased due to this construction. Thus, this structure is unsuitable for high speed engines. Further, if the width of the rib reinforcement is increased to provide proper rigidity for the piston skirt, the piston is subject to overheating.